The present invention relates to novel 2,3,-bis(dialkylaminophenyl)quinoxalines and their use as photoconductive substances in electrophotographic recording materials, in particular for lithographic and resist applications.
It is known to use quinoxaline derivatives as photoconductors in electrophotographic recording materials (German Pat. No. 1,254,469, equivalent to British Pat. Nos. 1,062,935 and 1,004,461). The light sensitivities exhibited by the quinoxaline derivatives described therein are, however, too low to meet high-standard requirements. Due to their rather poor sensitivity, electrophotographic recording materials containing these photoconductors are, for example, not very well suited for laser exposure, since no sufficient charge contrast between the exposed and unexposed layer areas is obtained. Even when conventional light sources are used, these recording materials are found to be less suitable, for even after a prolonged, intensive exposure their residual charge is undesirably high. This is the reason why exposed layer areas accept toner material in the developing step and, as a consequence thereof, the visible image obtained exhibits low crispness and poor resolution.
It is accordingly an object of this invention to provide photoconductors for electrophotographic recording materials having a higher sensitivity to light and higher image contrast.
This object and others are achieved by a 2,3-bis(dialkylaminophenyl)quinoxaline represented by the general formula ##STR2## wherein R is an alkyl having up to 4 carbon atoms, R.sub.1 is hydrogen or alkyl having up to a 4 carbon atoms, R.sub.2 is the same as or different from R.sub.1, and is selected from the group consisting of alkyl and alkoxyl having up to 4 carbon atoms, and R.sub.3 is the same as or different from R.sub.2 and is selected from the group consisting of hydrogen, alkyl and alkoxyl having up to 4 carbon atoms.
The objects of the invention are also achieved by a photoconductive substance useful in electrophotographic recording materials, comprising a 2,3-bis(dialkylaminophenyl)quinoxaline.